Although computer experts all over the world have analyzed the causes of the virus from different positions or angles, they have not been able to draw a conclusion. They can only speculate that computer viruses are due to the following reasons: first, the inspiration of science fiction; Second, the product of practical jokes; Third, the product of computer games; Fourth, the result of software property protection.
IT industry generally believes that computer viruses have gone through six important stages of development, from the most primitive single-machine disk virus to the mobile phone virus that gradually entered people's field of vision.
The first stage is the primitive virus stage. It is generally believed that the generation period is between 1986- 1989. At that time, because there were few computer application software, and most of them ran on a single computer, viruses were not popular in large numbers and the types were limited, so it was relatively easy to remove viruses. The main features are: single target; It mainly monitors the running state of the system by intercepting the system interrupt vector, and infects the target under certain conditions; Virus programs have no self-protection measures and are easy to be analyzed and dissected.
The second stage is the mixed virus stage. Its life span is between 1989- 199 1 year, which is the stage of computer virus from simple to complex. The application and popularization of computer local area network (LAN) brought the first epidemic peak of computer virus. The main characteristics of the virus at this stage are: the attack targets tend to be mixed; Take a more subtle way to stay in memory and infect the target; The virus has no obvious characteristics after infecting the target; Virus programs often take self-protection measures; There are many variants of the virus and so on.
The third stage is polymorphic virus stage. The main feature of this kind of virus is that most virus programs put into the host program are changeable every time they infect the target. Therefore, anti-virus software is difficult to kill. For example, the "ghost" virus in China 1994 belongs to this type. At this stage, virus technology began to develop in a multi-dimensional direction.
The fourth stage is the network virus stage. Since the middle and late 1990s, with the development of the Internet, a large number of mail viruses and macro viruses have appeared, which spread quickly, are concealed and destructive. That is, from this stage, the anti-virus industry began to sprout and gradually formed a large-scale emerging industry.
The fifth stage is to actively attack the virus. Typical representatives are the "shock wave" virus that appeared in 2003 and the "shock wave" virus that prevailed in 2004. These viruses take advantage of the loopholes in the operating system to spread wildly, without any media or operation, and users may be infected as long as they surf the Internet. Because of this, the virus is more harmful.
The sixth stage is the "mobile phone virus" stage. With the development of mobile communication network and the continuous strengthening of the function of mobile terminal-mobile phone, computer viruses began to enter the world of mobile communication network from the traditional Internet. Compared with Internet users, mobile phone users have a wider coverage and a larger number, so once the high-performance mobile phone virus breaks out, its harm and influence are greater than those of Internet viruses such as "shock wave" and "shock wave".